The present invention relates generally to systems for forming concrete structures. More specifically, the present invention relates to an all steel overhang system for use when forming an overhanging portion of a concrete structure, such as a portion of a bridge deck or a floor, and that protrudes in cantilever fashion from a supporting structure.
In concrete construction modular forming systems for forming concrete walls are generally well known in the art. Modular forming systems for concrete walls are generally favored by contractors because such modular systems permit the rapid assembly, disassembly, and reuse of the forms, thus offering significant savings in terms of time, labor, and materials. Moreover, the use of a discrete number of pre-manufactured wall form sections permits the construction of wall having different height, length, and thickness simply by choosing modular sections of the desired size.
When constructing bridges having concrete bridge decks, frequently a portion of the bridge deck will be constructed so as to extend outwardly from the outermost beam or girder in cantilever fashion. Of course this overhanging or cantilevered portion of the bridge deck must be properly supported from below by formwork so as to support the uncured concrete.
Typically, the temporary support of uncured concrete is achieved by first individually constructing a number of cantilevered support members. These cantilevered support members are then attached to the outermost beam or girder in outwardly extending fashion. Next, a number of longitudinal supports, most typically wooden members, are placed across the cantilevered supports in a direction parallel to the beam or girder. The formwork is then constructed on top of the wooden members.
After the concrete has been poured and is adequately cured, the form system and the supporting members are disassembled one-by-one. Such a conventional approach is very labor intensive, time consuming, and expensive both before and after the concrete has been poured.
It would be desirable to extend the cost savings afforded by modular construction of wall forms to the modular construction of overhang supports systems. Preferably, such a modular or ganged overhang forming system would permit the placement and/or removal of the system in discrete segments, such as by using a crane. Such modular or ganged construction of concrete overhangs would greatly improve the efficiencies associated with the construction of such overhang systems.
A ganged overhang form system constructed in accordance with the teachings of the present invention permits the placement and removal of overhang forms in ganged or modular sections. In the disclosed embodiment, such sections may be, for example, up to twenty four feet (24xe2x80x2) in length. Longer and shorter sections may be contemplated. In the disclosed embodiment, each section may typically include a pair of frames, each of which may be secured by a hanger to a support structure, such as a bridge girder on a bridge under construction. The section will include a form panel already in place and spanning the distance between the frames. Each section may further include, by way of example and not limitation, at least one of the following: 1) edge forms, with or without optional plates for forming drip strips in the edge of the concrete; 2) guardrail attachments; 3) cross-bracing; and/or 4) supporting legs. Once the ganged form sections are assembled, the sections may be placed and removed using a xe2x80x9cCxe2x80x9d hook without disassembly, thus offering tremendous cost savings compared to more conventional approaches.